Large mature trees in the urban landscape have witnessed many weather events, seasonal fluctuations, and the stripping and pollution of our natural, once-forested soils. They have stood through all of these events while still providing us with many environmental, economic, aesthetic, and mental benefits. It is only right as stewards to help them reach the next phase of their life cycle.

 

Caring for mature trees that have spanned decades (and sometimes many generations) is much different than managing younger, more vibrant trees. Many times the best prescription is constant observation of these large specimens so that we can potentially catch any issues before they become detrimental to the health. If we determine that there is no prescription needed, we continue to monitor them every year and adjust the treatment plan as needed.   

 

If we notice issues within the canopy or surrounding root zone, we begin with a soil sample to determine if there are nutrient deficiencies. Providing the tree with the appropriate nutrients, soil, pH, and soil porosity is paramount. These giants require enormous amounts of water and nutrients to maintain their vigor and vitality. As we continue to expand our urban sprawl, our native forested soils become less and less nutrient rich and our current urban soils become more compacted.

 

When it comes to pruning, we also take a different approach. Our primary focus is to mitigate as much risk by just removing dead material within the canopy and only pruning live branches when necessary. Ideally, we like to leave as much foliage on mature trees to allow them to transpire and respire. Yes, mature trees transpire, and they do so in large quantities. Transpiration is the process where water is released from the leaves as water vapor, and it's a crucial part of the water cycle and the tree's life processes. A large oak tree, for example, can transpire up to 40,000 gallons of water per year. This process helps to cool the tree's leaves and transport nutrients throughout the canopy. 

 

Risk mitigation is another aspect of our mature tree prescriptions. Many times these trees have displayed cavities or unfavorable branching structures that, if left unattended, could cause potential harm to people and objects. Risk reduction pruning, along with potential structural support systems, greatly mitigate the risk associated with some of the issues within the tree.

Our end goal for any of our mature trees is to keep them around for future generations to enjoy.  In the words of Robert Louis Stevenson, “It is not so much for its beauty that the forest makes a claim upon men's hearts, as for that subtle something, that quality of air that emanates from old trees, that so wonderfully changes and renews a weary spirit.”